Thank you guys. The black is just a hole drilled with a forstner bit and after the top is routed out for the phone to fit I drilled a 5/16” hole to connect the two. It directs the sound from the phones speaker out the hole in the hardwood and yes it does sound great.

@7footer – thank you! I could not figure out what that little piece of wood on the front was for – now I see it’s what you said – a cut off segment of a guitar body and that’s the bridge. Now I like it even better – I know a guitar player who needs this as a gift.